A 28–40-GHz Digital Step Attenuator With Low Amplitude and Phase Variations

Abstract

This letter presents a 28-40-GHz 5-bit digital step attenuator (DSA) in a 0.13-μm SiGe BiCMOS technology. The DSA achieves low amplitude and phase variations by using the following techniques: 1) combination of distributed, T-type, and modified π-type attenuators can ensure a low amplitude variation while maintaining a compact size; 2) interstage matching is designed to relax the loading effect between each stage; 3) inductive compensation is adopted to reduce the phase error for 8- and 16-dB attenuation cells. The DSA exhibits a 31-dB tuning range with 1-dB tuning step. The measured rms amplitude and phase errors are <; 0.43 dB and <; 5.4° over 28-40 GHz, respectively. The insertion loss is 5.4-9.1 dB from 28 to 40 GHz.